The issue was not with the CLAC, but rather the fact that the forge2.runtime ClassLoader did not contain the necessary classes, thus the CLAC did not know of their existence, and created a proxy with no interfaces.
Addon APIs must be added to the forge2.runtime module. If this is an issue, and other JBT/Eclipse UI extensions need their classes made available (say for an extension API), we will need to re-visit the way in which we are instantiating the CLAC and see if it still makes sense. We may need to add a CLAC extension point to allow making a given invocation with the TCCL (or fall back to the TCCL if nothing else resolves, currently we ignore TCCL.)
Until then, the above is what must be done.
--
Lincoln Baxter, III
http://ocpsoft.org"Simpler is better."